not "cannot change job"

After 485 pending for more than 180 days, primary applicant can change job in another company, or change multiple jobs since then. He/she does not have to stick to same company after GC approved. He/she can change jobs to another company in same/similar field in order to fulfil the original commitment that he/she will work for the position where GC is issued as a prospective contribution. Usually CIS will issue RFE to verify his commitment during 485 pending.
When he/she obtains GC and then quickly become non-employed, this adverse effect will apply on his GC-pending spouse, or his future citizenship application.

Spouse is always eligible to hand-in 485 when primary's PD becomes current.

PJ's blog has details interpretation.